Final Project on power plant

8/11/2019 Final Project on power plant

1/58


2/58

ACKNOWLEDGEMENTACKNOWLEDGEMENTACKNOWLEDGEMENTACKNOWLEDGEMENT

We Shilajit Saha and Sourav Das of Seacom Engineering College , Howrah affiliated toWest Bengal University of Technology are honored and thankful to Damodar ValleyCorporation for letting undergo this training program at Durgapur Thermal Power Plant at Waria for 28 days from 24 th June 2013 to 20 th July 2013 .

We are also thankful to The Personnel Manager (B) Mrs Gopa Chakaravarty for selectingus for this Training Program.

We pay our sincere gratitude to the following persons who have guided us in this trainingprogram.

Mr C. Mondal (ES-II)Mr A. Bhattacharjee (Exec. Engg)

Mr Vivek (Exec. Engg)

Mr D. Mondal (Asst. Engg)

Mr Santosh Kumar (Asst. Engg)

Mr N. Banerjee (Senior Engg)

Mr S. R. Chatterjee (Asst. Controller, Mechanical Dept.)

For lending their precious time in enhancing my technical knowledge

We are also thankful to all other Employees of this concern for clarifying my doubts in thistraining program.

And at last but not the least we are also thankful to our Principal Dr Rajiv Bag for grantingus this training.

__________________________

Mr C.Mondal

Electrical Superintendent II


3/58

CONTENTSCONTENTSCONTENTSCONTENTS ABOUT DAMODAR VALLEY CORPORATION DURGAPUR THERMAL POWER PLANT INTRODUCTION COAL HANDLING PLANT WATER TREATMENT PLANT DEMINARALIZATION PLANT BOILER AND ITS AUXILARIES TURBINES ASH HANDLING PLANT GENERATOR COOLING SYSTEM MAIN ELECTRICAL EQUIPMENTS MOTORS IN IMPORTANT FANS IMPORTANT MOTOR SPECIFICATIONS SWITCH YARD SYSTEM INSTRUMENTATION AND SAFETY

PRECAUTIONS LABORATY AND SECURITY COMPARISON B/W U#3 AND U#4 ENVIRONMENTAL ASPECT CONCLUSION


4/58


5/58

:

Sl. No Name Capacity(MW)

1 Tilaiya Dam 4

2 Maithon Dam 63.2

3 Panchet Dam 80

Gas Based Power Plants:


1 Maithon Gas Turbine 82.5

Thermal-Coal Based (Joint Ventures):


1 Bokaro Power Supply Corporation Ltd. 302

2 Maithon Power Limited 1050

Joint Venture Projects :

Maithon Power LimitedA joint venture company by DVC and Tata Power has been formed to implement 1050 MW MaithonRight Bank Thermal Power Project for meeting the energy needs of power deficient regions on exportbasis.Bokaro Power Supply Corporation Limited (BPSCL)A joint venture company of DVC and SAIL has been established to operate and maintain the captivepower and steam generation plant, hived off by SAIL and its Bokaro Steel Plant and supply powerand steam exclusively to Bokaro Steel Ltd.DVC EMTA Coal Mines LimitedA joint venture company formed with Eastern Minerals & Trading Agency for development andoperation of Captive Coal Mine Blocks and supply o f coal exclusively to DVC Thermal PowerProjects of 10th and 11th plan .Mining & Allied Machinery Corporation (MAMC)The Mining and Allied Machinery Corporation (MAMC) in Durgapur one of the PSU's in India set upunder the rupee -rouble agreement and enjoying Soviet patronage in the early sixties. Bharat EarthMovers has the highest stake (48%) in the consortium while the other two PSUs DVC and Coal Indiahave 26% stake each.


6/58

Durgapur Thermal Power StationDurgapur Thermal Power StationDurgapur Thermal Power StationDurgapur Thermal Power Station(D.T.P.S), DVC(D.T.P.S), DVC(D.T.P.S), DVC(D.T.P.S), DVC

D.T.P.S is one of the many power stations under DVC and it is located at Waria, Durgapur. Thispowerplant is presently installed wit h a capacity of 350 MW, comprising U#3 of 140 MW and U#4210 MW.

U#3 is provided with M/S ABL make boiler & M/S GE, USA make T.G, was commissioned in Dec,1966 and U#4 of M/S BHEL make boiler & T.G commissioned in Oct, 1982. It may be noted thatU#1 and U#2 of D.T.P.S was decommissioned in Oct. 1985 due to severe fire damage.

The U#3 is capable of generating at 56% PLF. For further improvement, R&M/LU action has beentaken up, so that it can generate at about 70% PLF.

The U#4 is running at an average PLF of 50% or more. D.T.P.S is located near the Grand TrunkRoad, Waria railway station, and River Damodar. Thus, it is well connected by rail and road forbringing coal, oil and other raw materials and river Damodar supplies adequate water for the smoothrunning of the plant.

The main input materials are: -

1 . Coal (Supplied by Eastern Coalfields Limited at Raniganj , Jharia, etc. )

2 . Crude Oil, Viscous Oil ( Supplied by Indian Oil Corporation Limited)

3 . Water (From river Damodar through Durgapur Barrage)

The main components of the power plant are: -

1. Intake Pump House 9. Boiler, Turbine, Generator, Transformer and Auxillaries

2. Water Treatment Plant 10. Switch Yard

3. Demineralisation Plant 11. Instrumentation and Control

4. Cooling Tower 12. Compressor House

5. C W Pump House 13. Pumps

6. Coal Handling Plant 14. Stores

7. Ash Handling Plant 15. Ancillary Facilities

8. Fuel Handling Plant 16. Laboratory & Workshop


7/58

Introduction: Thermal Power Plant Introduction: Thermal Power Plant Introduction: Thermal Power Plant Introduction: Thermal Power Plant A power plant is assembly of systems or subsystems to generate electricity, i.e, power with economyand requirements.A thermal power station is one that takes chemic al energy and forms heat (therm) and then converts

that heat into electrical energy. Here, the prime m over is mainly steam driven. Water is heated, turnsinto steam and spins a steam turbine which drives an electrical generator. After the steam passesthrough the turbine, the steam is condensed in a condenser. This principle is known as Rankin eCycle. The waste heat from a gas turbine can be used to raise steam in a combined cycle plant thatimproves overall effectiveness.

But for better performance and greater efficiency, a modification of Rankine Cycle, i.e. RegenerativeCycle is used. In this case, ste am is extracted at certain points during its expansion and using thissteam, the feed water is heated, due to which, the amount of overall heat rejection decreases, and sothe efficiency of the power plant increases. For this reason, D.V.C D.T.P.S uses Regenerative feedheating process for running their power plant.


8/58

COAL HANDLING PLANTCOAL HANDLING PLANTCOAL HANDLING PLANTCOAL HANDLING PLANTI ,

. D. . . I .

10 1 . , #3 1400 #4 2100 .

I C , , . :

C F (EC ) D. .C

C

(B C B )

/ D

C B A

H C

C C

B C B

( 1 )

B B

(3 )

B

(6 )C

F

C F . B C C

( B C )

C


9/58

DIFFERENT PARTS OF C.H.PDIFFERENT PARTS OF C.H.PDIFFERENT PARTS OF C.H.PDIFFERENT PARTS OF C.H.P

1. COAL HOPPER : C , , .F , .

. . , , ( )

. & 2 . 250 / .

2. CRUSHER: I 25

. . &


10/58


11/58


12/58

Water Treatment Plant Water Treatment Plant Water Treatment Plant Water Treatment Plant The water treatment plant is an important sector of a thermal power plant. It is here the rawriver water is treated and made gradable for usage in plant boiler and other auxiliary purposes

in the plant and area around.In D.T.P.S the main source or the river water is river Damodar . The water of the river,known as the Raw water, contains many impurities, like

1. Gases causing erosion and corrosion of metal

2. Hard salts leading to overheating by forming hard scales.

3. Soft salts forming scales and dissolved solids.

4. Organic matters, silt, clay, silica and other impurities in colloidal form.

Various steps are taken to eliminate these impurities and prepare usable water.

In DTPS, Unit #3 and Unit#4 has almost identical type of Water Treatment Plant, but that ofUnit #4 is a bit of modernized.

Sectors of the Water Treatment Plant :-

Raw water Pump house or intake pump house Aereator Chlorination & Alum solution sector Clariflocculator chamber

Gravity filter bed Filter water & clear water storage tank Then to the different required sectors


13/58

Layout of the Water TreatmentLayout of the Water TreatmentLayout of the Water TreatmentLayout of the Water TreatmentPlant Plant Plant Plant

CHLORINATION+ALUM SLUDGE TO CANEL

AE EA

C EA A E

C. . C. .

B

C

CC

C

B

A


14/58

DEMINEDEMINEDEMINEDEMINERALIZATION PLANTRALIZATION PLANTRALIZATION PLANTRALIZATION PLANT

. . I , . . I , . :

1. AC A CA B : I , ,

. I , , .

2. CA C C A : A , (C ++ ++ ) H + .

( 3 H). A , , .

2 3 + 2+ ( 3)2 + 3

+

A , . A A H A

.

( 3)2 + 2 4 4 + 2 3

A , . C , B ,, , .

3. A C C A : , ,

. H. , 4, . . B , , .

3 + C 3 C + 2I , H.

3 C + 3 + C


15/58

4. B : I , ,

. . I

.

.B: I , 100%

1. 6.82. 3. 0.01 .

. . .


16/58

BOILER & ITS AUXILARIESBOILER & ITS AUXILARIESBOILER & ITS AUXILARIESBOILER & ITS AUXILARIES

In Boiler, steam is generated from D.M water by addition of heat. The heat has two

part.viz sensible & latent heat. The boiler is based on Modern Rankine Cycle withregenerative and reheating process. The sensible heat raises the temperature & pressureof both water & steam. The latent heat converts water into steam. This conversiondepends on pressure & temperature.


17/58

A A : In the D/A, the condensate, while flowing, gets exposed in the traysto maximum the surface for efficient scrubbing for liberation of gases (mainly oxygen)when the steam flows in opposite direction. Condensate is heated up and liberatedgases move upward with steam & later escape to atmosphere, while the steam getscondensed. The condensate is admitted at the top of the deaerating columns and flows

downwards through the spray valves.

A A A A : Deaerator storage tank serves as storage forfeed water in between the condenser hot well and boiler drum, the boiler drum andcondenser hot well levels are independently maintained within a preset limit at allloads. Therefore, in case of a sudden change of load either some amount of water is to


18/58

be added in the cycle or some amount is to be removed. Deaerator storage tankprovides this extra amount of water to the feed pump when required due to highersystem demand and also absorbs some amount of water from the cycle when the loaddemand is reduced.

A A C C A : To ensure proper and initial mixing and heatingof the deaerator tank water with pegging steam, a recirculation is provided from D/Adischarge (BFP suction header) to steam space of the condenser with isolating andregulating valves. The condensate pump, when the recirculation is put into service,must be kept running. It also helps in cooling down deaerator quickly on unit trip outsto eliminate dangerous line and D/A water hammering, and also the danger of losingthe required NPSH for feed pumps.

C : . F , . F

. ( ) .

1 14 . F H.

. ( HH 1 & HH 2). A I. . F , I. . . . , . .

.

B : B , . .

. ,

.

. A : Super heater is composed of four stages or sections, a platen

section, pendent section, rear horizontal section and steam cooled wall and roof androof radiant section. Each of these is composed of several assemblies spaced at givendistance and enters across the width of furnace .

A : The reheaters are composed of two stages or sections, the frontpendant vertical spaced section and the rear pendant vertical section. The front sectionhas 59 assemblies and rear has 89 .


19/58

A C : The purposes of main ejector is to maintain vacuum in thecondenser (approximately 696 mm. ).This is done by auxiliary steam, which whenflows through the nozzle of ejector creates a pressure drop that sucks the air insidecondenser. In the process the auxiliary steam is condensed by water from CEP& is sentto hot well. The water from main ejector flows towards gland coolers .

A C 1: Gland cooler-1 is provided to suck & cool air steam mixture& condense the steam from gland seals of HP, IP & LP (front & rear). It employsauxiliary steam and nozzle to create the necessary vacuum for suction. The steam iscondensed by condensate from ejector. In the process water is heated & steam iscondensed into water is heated & steam is condensed into water & retained in the hotwell & air is exhausted.

A 1: LPH-1 is divided into 2 parts, each of which is located inside upperpart of each condenser. Water from GC-1 comes to LPH-1 & after heating to a certainlevel passes to GC-2.

A C 2 : This gland cooler has been designed to condense the steamfrom gland seals HP 3&2, IP 2&1 (F&R). The construction of this cooler is identicalwith LPH-2, 3, 4. The Gland coolers are directly fitted without any valve. That means,if the gland cooler stops functioning, then the whole unit will trip.

A (2, 3, 4): These heaters are vertical surface typewhere condensate flow through U shaped tubes & steam flows over the tubes. In thisprocess the condensate is heated and steam is condensed.

. A : The drip of L.P heater 1 is transferred to hotwell by means of a5 M loop seal. The drip from LP heaters (2,3,4) is cascaded from one heater to next lowpressure heater. I this way, drip from LP heater No.4 is cascaded to LP heater No.3,


20/58

drip from LP heater no.3 is cascaded to LP heater No.2. In case the next low pressureheater is out of service, then the drip can be transferred to the subsequent low pressureheater. The total drip collected in the LP heater No.2 is fed back into the maincondensate cycle after LP heater No.2 during normal operation through two 100%capacity drip pumps. Normally one pump is adequate. The pump control system isdesigned in such a way that pump can be on remote manual or on automatic. Thedischarge valve of the drip pump is controlled by one low level controlled by one of thedrip pumps is running. During low load operation, drip level in LP heater No.2 iscontrolled by a separate high level controller and the drip is drained into the condenser.LP heater No.4 normally operates with steam from turbine Ext.No.4. It also receivessteam from Aux. steam heater a pressure regulator. Drip level in GC NO.2 iscontrolled by its own controlled by its own controller and the drip is drained to themain condenser hot well. Drip level in GC NO.1 is maintained by a loop and drained tothe drain expander; drip from main ejector is cascaded to the next two pressure stagethrough suitable loops 8M and 5M and finally drained to condenser by a 3M loop. LPheater No.1 is a horizontal surface type heater in two halves, each half has been locatedinside the upper part of each condenser. Two halves have been installed in parallel &

the steam to both is supplied from the same extraction point. The U shaped tubes are ofsolid drawn admirality brass. 19 mm external dia, 1 mm and .75 mm thick and areexpanded by rolling into the tube plate at both the ends. Partitions have been providedin the water box to make it a 4 path design. The main condensate flows through thetubes in four paths before leaving the heaters. L.P. heater 2, 3, 4 are identical inconstruction of LP heater No. 1, but are of vertical surface type.

C : In D.T.P.S, there are two condensers one for unit #3 and the other forunit #4. The condenser of the Unit #3 runs in an open cycle, whereas that of unit #4runs in a closed cycle.In open cycle, water comes from river Damoder, cools, and then goes back to the river.Its a simple process. But as the water comes from river, it often carries garbage thatblocks the condenser. For that reason, the unit #3 has reverse flow facility for cleaningoperation.In closed cycle condensation, cooling water comes from cooling tower. For that reason,it does not need any reverse flow provision.The condenser is divided into two parts. The first part being divided into upper half andlower half. The steam coming out of the Low Pressure Turbine has to be condensed.This condensed water has to be fed into the main power cycle so that the cycle carriesout uninterrupted.


21/58

C C C A C : The condensing phenomenon hasto be brought about by a separate cycle known as Cooling Cycle. The Cycle consists ofa condenser along with a cooling tower and a storage tank. A.C.T make up pump isalso needed to counter the loss of cooling water in the cycle.With the help of C.W pump, the water from the storage tank comes to the lower righthalf of the condenser compartment. This water gets heated and cools the steam. Theheated water then moves to the adjoining compartment and as a result of force due tothe pressure and decrease in density due to increase in heat addition.

FURNACEFURNACEFURNACEFURNACEIt is main part of power plant in which water is heated and converted into steam. InD.T.P.S. U- draft type furnace is used in unit #4.There are six mills, each mill have four coal feeding pipes. These pipes are sent to eachvertical edge of furnace. With the help of these pipes, coal is fired tangentially into thefurnace. The coal is easily sucked into the furnace from mill because furnace is kept inNegative Pressure with the help of I.D Fan.In D.T.P.S, vertical edge furnace is divided into 12 parts. If mill 1 is in service, then oilgun would be in service. Near oil gun mouth electric igniters are arranged.

An industrial furnace or direct fired heater is equipment used to provide heat for aprocess or can serve as reactor which provides heats of reaction..


22/58

Furnace designs vary as to its function, heating duty, type of fuel and method ofintroducing combustion air. However, most process furnaces have some commonfeatures.Fuel flows into the burner and is burnt with air provided from an air blower. There canbe more than one burner in a particular furnace which can be arranged in cells whichheat a particular set of tubes. Burners can also be floor mounted, wall mounted or roofmounted depending on design. The flames heat up the tubes, which in turn heat thefluid inside in the first part of the furnace known as the radiant section or firebox. Inthis chamber where combustion takes place, the heat is transferred mainly by radiationto tubes around the fire in the chamber. The heating fluid passes through the tubes andis thus heated to the desired temperature. The gases from the combustion are known asflue gas. After the flue gas leaves the firebox, most furnace designs include aconvection section where more heat is recovered before venting to the atmospherethrough the flue gas stack. (HTF=Heat Transfer Fluid. Industries commonly use theirfurnaces to heat a secondary fluid with special additives like anti-rust and high heattransfer efficiency. This heated fluid is then circulated round the whole plant to heatexchangers to be used wherever heat is needed instead of directly heating the productline as the product or material may be volatile or prone to cracking at the furnacetemperature.)

: Oil Gun is made of two concentric cylinders. The oil comes from outercylinder and steam comes from inner cylinder. Then they are mixing in a mixingchamber, due to this inter mixing, oil gets atomized. This atomized oil is easy to burnbecause it has large surface area.


23/58

C AC : Pulverized coal doesnt catch fireeasily. Hence coal needs specific heat to burn. It gets the specific heat due to burning ofcrude oil. When the mill is in service, then coal is fed to it through proper path. At the

same time hot air is passed through that keeps the pulverized coal in the air for sometime. At this same time the oil gun comes into function and provides the specific heat.Therefore, coal starts to burn. After that, oil feeding is controlled. The hot air sent tofurnace together with coal is called primary air and extra hot air sent to furnace throughthe passes is called secondary air.

TurbinesTurbinesTurbinesTurbines

TURBINES: There are 3 stages of turbines are used. They are high pressureturbine, intermediate pressure turbine and low pressure turbine. The H.P.T is thesmallest and the L.P.T is the largest. The boiler of unit #3 is ABL make, and that ofunit #4 is BHEL make. The IPT and HPT of unit #4 has control valves, which are camoperated, where as only H.P.T of unit #3 has control valves attached to it. The turbinesare well insulated and they are free at both top and bottom to allow their expansion.Steam, coming from the last super heater, flows in the main stream line and is dividedin two sub lines and enters the L.P.T via double entry mechanism. From there, it comesto the I.P.T and from there; it comes to the H.P turbine. The pressure graduallyincreases throughout the process and it enters H.P turbine at 146 kg/cm 2 and 540 o C.H.P turbine has 12 stages. The directions of steam flow in H.P turbine and I.P turbine is

opposite to each other. This reduces axial thrust on the bearings. The number of stagesin I.P.T is 11. The L.P turbine is a double action and has 4x2 numbers of stages. Thesteam flow rate through the turbines is 670 ton/ hr. The turbines are L.M.W type inDTPS unit #4 . HP & LP bypass system are also present in the turbine for protectionpurposes of generator.


24/58

TURBINETURBINETURBINETURBINE SUPERVISORY EQUIPMENTSUPERVISORY EQUIPMENTSUPERVISORY EQUIPMENTSUPERVISORY EQUIPMENT ::::The Turbine Supervisory Equipment or Turbovisory equipments are to provide informations relating to the operating condition of a turbine. Continuous supervision ofdifferent parts, which determine the operating reliability of the machine together with

operational safety is essential for smooth running of the power plant.In Turbovisory, the following main parameters are measured:

1. Axial shift2. Differential expansion of H.P, I.P, L.P turbine3. Overall expansion of turbine H.P, I.P casing4. Speeder gear position measurement5. Shaft eccentricity6. Speed7. Control valve servo motor position (CVSM)There are also certain inter locking system inside the power plant.

ASH HANDLING PLANTASH HANDLING PLANTASH HANDLING PLANTASH HANDLING PLANT (

80%) I D (I.D F ) 20% . . D ,

, , ( ), , , , , .

C A A A BOTTOM ASH HOPPER: It is a water filled hopper placed below the furnace water wall ring

headers to receive bottom ash generated out of combustion of coal. BAH is generally of two types Dry Bottom and Wet Bottom. In Dry bottom type, the BAH is keptempty prior to receiving Bottom ash and quenched by separate spray arrangement from inside. In thissystem continuous ash evacuation and disposal take place through and handling devices like Scrapperconveyer.The bottom ash hopper is generally filled with water which reduces the temperature of deposited hotash and clinkers. Sudden quenching also helps in disintegration of clinkers. The deposited ash in theform of granules & clinkers is taken out periodically.

ELECTROSTATIC PRCIPETATOR: A small part of fly ash gets deposited in the economizerhoppers before it takes entry to the ESP, majority fly is separated out.In ESP there are two sets of electrodes viz. collecting & emitting electrodes. The collecting electrodesis made up of steel sheets pressed or rolled to a special profile. The emitting electrode is in helicalform, they are arranged in alternative rows. A unidirectional high voltage from a rectifier is appliedbetween these two electrodes connecting its negative polarity to the emitting electrodes and positivepolarity to the collecting electrodes which are earthed because of the physical configuration, the


25/58


26/58

ELECTRICAL SYSTEM:

( ) ( C):

. EC

. , EC . A ,

. EC

. EC , .

EC .

:

BAPCON OPERATION: -

The ESP is pre-dominantly not a constant load to the thyristor control panel. The electrical fieldbetween the electrodes and thereby the ESP current' and 'voltages are influenced by the gascomposition, temperature and by the electrical properties of the dust Too high voltage, considering thecondition of the ESP. may cause very high spark rate. On the contrary a too low voltage will give alow precipitation:

BAPCON controls the precipitator power by changing, ignition angle of the thyristors. ESP Current,ESP voltage and zero crossing point of the primary voltage are used as input data. On switching 'ON'the T/R set, the BAPCON slowly increases the filter current towards the set current limit The T/Oaction over rides the start up time slightly at start. When a spark occurs the set current is reduced tozero and the thyristors are: blocked for 20ms. After restart of the thyristors. The current quickly'increases to a value which is slightly lower than the current at which the spark occurred. This currentdecrease is called STEP. After that, the current will rise slowly as per the setting in T- Control. Thevalues of S control and T control will decide the spark Rate.


27/58

SPARK RATE :-

The spark rate is determined by the. settings of S - Control' and T - Control.Suppose T - Control is set at 20% which corresponds to 2 minutes, the time required by theRECTIFIER to reach the rated current after a spark, from zero current will be 2 minutes. BAPCONwill however increase the current very fast up to S - Control level, and there after will follow T -control.

. 5% , . 5% (5% 2 ), 6 . I

(20 ) 6 . E . , .

Spark Rate = __________1000_________________S - Control (%) x T-control (%)

A C & , .

C A :

, . A

. , .

.

BA C , . .


28/58

200% E , . , .

. ( ) , . I . 5 .

, E .

BA C A :

I , . H , E

. / FF . E

, . / .

, .

.


29/58

C A A A :

E , E . BA C

. , I BA C .

. BA C .

. , BA C , E .

. .4.

I .. . . 8. I .

. . ED .


30/58

. ED DE .

. ED I EACED .

. FF : / .

.

B I I G : I .. : I .

10 2, 49 20 4.

BA C E .H 20 BA C , I ,

E .

13% .

A A C A (AC ):

AC E D , . AC ,

, , .

F :

H C

AC . F , . .

.


31/58


32/58

The various processes that take place in Ash Handling Plant are:

REMOVAL OF BOTTOM-ASH: .

. .

A A : F E. . , ,

.

.

DISPOSAL OF ASH SLURRY: .E .

250 3 , .


33/58

GENERATORGENERATORGENERATORGENERATOR COOLINGCOOLINGCOOLINGCOOLING SYSTEMSYSTEMSYSTEMSYSTEM

: A E G . . I , .

D , . I .

H . #3 D , D C .

But the generator of Unit#4 DTPS, DVC has a system known as the Generator Stator WindingCooling System .

The main features of this system are:

Generator is Hydrogen cooled

Hot Hydrogen in turn water - cooled.

Windings also water- cooled.

In this case, cold D.M water is circulated through the windings by hollow copper pipes.

Generator of Unit#4 has 2 oil seals and thrust seals , while that of Unit#3 has axial seals instead ofthrust seals. The oil seals get their supply through 4 pumps: Main Oil Pump of turbine, Starting OilPump, A.C Oil Pump and D.C Oil Pump.Generator lubricating oil is supplied from Dumper Oil Tank (Yellow in colour).


34/58

HYDROGEN COOLING SYSTEM OF GENERATOR

STATOR WATER COOLING SYSTEM


35/58

MAIN ELECTRICAL EQUIPMENTSMAIN ELECTRICAL EQUIPMENTSMAIN ELECTRICAL EQUIPMENTSMAIN ELECTRICAL EQUIPMENTS

210MW TURBO GENERATOR UNIT #4210MW TURBO GENERATOR UNIT #4210MW TURBO GENERATOR UNIT #4210MW TURBO GENERATOR UNIT #4SPECIFICATIONSSPECIFICATIONSSPECIFICATIONSSPECIFICATIONS

Rated KW Capacity : 210000 KW

Rated KVA Capacity : 247000 KVA

Rated Terminal Voltage : 15750 V

Rated P.F. : 0.85 Lag

Rated Stator Current : 9050 A

Rated Stator Voltage : 15750 V

Rated Rotor Current : 2600 A

Rated Rotor Voltage : 310 V

Rated Speed : 3000 rpm

Rated Frequency : 50 Hz

Efficiency : 98.4%

Excitation Current : 2600 A

Excitation Voltage : 310 V

Insulation Class : B

Phase Connection : Double Star (Y-Y)

Cooling Type : Hydrogen & Water Cooled

Gas Pressure : 35 Kg/cm 2

Serial Number : 10017

Makers Name : BHEL, HARDWAR (1977)


36/58

250 MVA GENERATOR250 MVA GENERATOR250 MVA GENERATOR250 MVA GENERATORTRANSFORMER UNIT #4TRANSFORMER UNIT #4TRANSFORMER UNIT #4TRANSFORMER UNIT #4

SPECIFICATIONSSPECIFICATIONSSPECIFICATIONSSPECIFICATIONS

Rated Output : 250 MVA

KV at High Voltage : 230 KV

KV at Low Voltage : 15 KV

Current Ratings HV : 627 A

LV : 9623 A

Frequency : 50 Hz

Impedance Voltage : 13 78 V

Connection Type : Yd1

Cooling Type : Air and Oil Cooled

Serial No : 6004124

Makers Name : BHEL, BHOPAL (1979)


37/58


38/58

12.5/15MVA STATION RESERVE12.5/15MVA STATION RESERVE12.5/15MVA STATION RESERVE12.5/15MVA STATION RESERVETRANSFORMERTRANSFORMERTRANSFORMERTRANSFORMER

SPECIFICATIONSSPECIFICATIONSSPECIFICATIONSSPECIFICATIONS

Rated Output : 12.5/15 KVA

Frequency : 50 Hz

HV Star KVA : 50000

(No-load) Volts : 138000

Rated Current : 209A

MV Star KVA : 45000

(On-load) Volts : 33000

Rated Current : 787A

LV Delta KVA : 125000

Basic Impedance Level (KV) :

HV Line : 650

HV Neutral : 110

MV Line : 200

LV Line : 50

Impedance (Volts) :

HV Line : 145000 KVA, 14.00%

HV-LV Line : 25000 KVA, 6.85%

MV-LV Line : 2500 KVA, 2.52%

Insulation Type : HV Winding Insulation Graded Down to Neutral

Cooling Type : OFB


39/58

6.6 KV SWITCH GEAR6.6 KV SWITCH GEAR6.6 KV SWITCH GEAR6.6 KV SWITCH GEARSPECIFICATIONSSPECIFICATIONSSPECIFICATIONSSPECIFICATIONS

Rated Voltage : 6.6 KV

Max Voltage of breaker operation : 7.2 KV

Frequency : 20 Hz

Current Ratings of Breaker :

Continuous : 2000 & 788 A

3 Sec r.m.s. : 44KA & 38 KA

Interacting Capacity :

Symetrical : 44KA

MVA (symmetrical) : 500 MVA

Asymmetrical capacity : 53 KA

Making Current : 123 KA

No. of Breaks per Phase : One

Insulation Level of Breakers :

1 min dry withstands : 35 KV

Impulse withstands : 75 KV

Type of closing : Electro-phenmatic Spring

Type of tripping : Shunt trip Electro-phenmatic

Operating air pressure : 16 Kg/cm 2

Storage air Pressure : 30 Kg/cm2

Makers Name : Hindustan Brown Boveri Ltd.


40/58

AUTOAUTOAUTOAUTO----TRANSFORMER RATINGSTRANSFORMER RATINGSTRANSFORMER RATINGSTRANSFORMER RATINGSSPECIFICATIONSSPECIFICATIONSSPECIFICATIONSSPECIFICATIONS

Rated Output (KVA) :

HV : 75000/105000/150000

MV : 15000/21000/30000

LV : 15000/21000/15000

Volts At No-Load :

HV : 230000

MV : 138000

LV : 7500

Current Ratings :

HV : 188/264/377A

MV : 314/439/628A

LV : 1155/1617/2309A

Type of Cooling : ON/OB/OFB

Frequency : 50 Hz

Impedance Voltage :

HV-MV : 17.04%

HV-LV : 61.56%

MV-LV : 43.17%

Connection /type : Y, y0, d1

Makers Name : Transformers & Electricals Kerala Ltd.


41/58

EXCITATION TRANSFORMEREXCITATION TRANSFORMEREXCITATION TRANSFORMEREXCITATION TRANSFORMERRATINGSRATINGSRATINGSRATINGS

SPECIFICATIIONSSPECIFICATIIONSSPECIFICATIIONSSPECIFICATIIONS

HV : 15000 KV

Terminals : H1/H2/H3

LV : 495 V

Terminals : X1/X2/X3

Volts : 15750/15375/15000 /14625/14250

Amperes : 38.9/39.8/40.8/41.8/42.9

%Rated Voltage : 105/102.5/100/97.5/95

Connect Each Phase : 1-2//2-3/3-4/4-5/5-6

Rated Output : 1060 KVA

Frequency : 50 Hz

% Impedance at 150 deg : 6.04

Base KVA : 1060

Type (K) Class : ANN

Encl. Type : NEMA2

Cooling Type : Air-Blast Cooled

Makers Name : Hammon Power Solution


42/58

Motors in Important FansMotors in Important FansMotors in Important FansMotors in Important Fans

Name ofthe fans

Typesofcooling

MakersName

KW/HP Volt(KV)

Fullloadcurrent(A)

RPM InsulationClass

ConnectionType

Induced

DraftFan

CACA BHEL 1300 6.6 140.5 740 F Y, Squirrelcage induction

motor withD.O.L starter

ForcedDraft

Fan

CACA BHEL 800 6.6 85.4 1490 B Y, Squirrelcage induction


PrimaryAir Fan

CACA BHEL 1250 6.6 132 1485 B Y, Squirrelcage induction



43/58


44/58

C.W. Pump Motor:

Rated Voltage, Phase, Frequency : 6.6 KV, 3 phase, 50Hz

Output : 1200 KW

RPM : 490

F.L. Current : 140 A

No load Current : 54 A

F.L. Efficiency : 99.8%

Starting Current : 500% of F.L. current

Starting : DOL

Insulation Type : B

Connection Type : Y

Manufacturer : BHEL, BHOPAL

Ash Water Pump Motor:

Rated Voltage, Phase, Frequency : 6.6 KV, 3 phase, 50Hz

Output : 243 KW

RPM : 1000

F.L. Current : 26.5 A

Insulation Type : B

Connection Type : Y

Cooling Type : CACA

Manufacturer : Kirloskar Electric Ltd.


45/58


46/58

THREE BUS SCHEME:

Two nos. main bus and one no. transfer bus gives greater degree of shutdown flexibility andcontinuity of service in case of bus outage by discriminative tripping of faulty bus . However, suchscheme is used where the extra cost is justified for this extra reliability .

ONE AND HALF BREAKER SCHEME : FIGUREFor every two circuits only one spare breaker is provided . The protection is however complicatedsince the central common breaker should associate with the right feeder, whose breaker is to be takenout of service .

TYPE OF BUS BARS

Rigid bus bar: In this type, tubular conductors are used for bus-bars and for making connectionbetween different equipments . Such bus bar has high rigidity, ease of clamping, resistance toswinging, reduced corona loss etc. but suffers from high comparative cost, traveling vibration along

jumpers, bus and equipments .

Strain bus-bar: ACSR conductors are strung with sag compensating spring between supportingstructure, spanning ground mounted equipments and circuits . Bundled conductors are used for highratings of bus-bars and reduced corona . However, aluminium pipes are employed whenever rigidconnections to different equipments are needed.

Care should be taken to use suitable bi-metal connectors / strips, whenever copper to aluminiumconnection are needed.

SWITCHYARD EQUIPMENTS :

Isolators: Isolators are used for no-load opening and closing of circuits . They can be operated from

remote by motorized, hydraulic or pneumatic mechanism. Three poles are either mechanically orelectrically ganged and may be provided with earth switch having either mechanical or electrical

interlock or both for safe operation only during de-energized condition . The isolators are interlockedwith circuit breaker for their operation while breaker status is Off only . This electrical interlock isachieved by isolation of D.C control power of isolator at ON position of breaker . The isolators are oftwo types :-

Centre-break type: Two arms rotate in horizontal plane to engage or disengage the contacts .

Centre rotating type: It makes a very stable contact, but the cost is higher than that of the centrebreak type for use of three insulators .

Isolators have their positional switches at their mechanism boxes for development of a set of contactsaccording to ON or OFF status of the isolators and these contacts are employed for differentsafety and operational interlocks as well as selection of proper voltage and current sources forprotection and metering .

CIRCUIT BREAKER: Circuit breakers are designed to operate in faulty condition of circuit, andhave rated making and breaking capacities in MVA . Making capacity is decided by consideration ofasymmetrical making current during closing of circuit breaker in an already short circuited line .


47/58

Therefore, calculation of fault MVA by network analysis is essential for selection of circuit breaker tobe of adequate capacity .

According to arc quenching medium, circuit breaker is of three types for switch-yard application .

MINIMUM OIL CIRCUIT BREAKER: Arc is extinguished in axial/cross jet explosion pot, where

arc is interrupted by axial / cross jet of oil produced by pressure developed due to vaporization of oil. Thus the energy of arc extinction is developed by the medium itself and no secondary arrangement is

required . By cascading the interrupter units, voltage grade of such breaker can be increased .

AIR BLAST CIRCUIT BREAKER: Arc is extinguished by blast of compressed air, which takesaway heat and deionizes the medium . Therefore, compressed air plant and piping system are requiredfor this type of breaker and add to the maintenance vagaries by leakage of air, breakdown ofcompressor etc .

SF-6 CIRCUIT BREAKER: As SF-6 is the strong electro-negative gas, it is de-ionized and recoversbreakdown voltage rapidly, and arc extinguishes at natural current zero . Zero current interruption isthe excellent feature, which makes it free from any current chopping, high TRV and restriking . Therefore, no damping resistance is required to control TRV . However, pre-closing resistor are used,when such breaker are employed in long transmission line of comparatively high voltage, to controlvoltage surge during closing of breaker .

On the contrary, MOCB and ABCB are having inherent problem of current chopping and need ofdamping resistance .

Breaker are operated by spring energy or where more energy is required either by hydraulic or bypneumatic energy .

As pressure of gas, hydraulic oil or compressed air affects the performance of breakers, some safetyinterlocks are provided to inhibit operation of breakers, when such pressures drop below the safetylimit . Such condition is called lock-out of breaker, and according to different set values of pressure,there are some closing lockouts and some tripping lockouts . Immediately, after appearance of anytripping lock out, the breaker should be by-passed by the bus-tie breaker and transfer bus, and thedefective breaker should be taken out of service .

SF 6 Gas Circuit Breaker Ratings:

Rated Voltage : 145 KV

Rated Impulse withstand Voltage : 650 KV

Rated power Frequency Voltage : 275 KV

Rated frequency : 50 Hz

Rated Normal Current : 2500 A

Rated Short time Current : 40 KA


48/58

Rated Short Circuit Duration : 3 Sec

Clear Factor : 1.5

Breaking Capacity :

Symmetrical : 40 KA Equivalent : 10000 MVA

Symmetrical : 40 KA

Line charging Current : 50 KA

Rated Making Current : 100 KA

Rated Trip Coil Voltage : 250 VDC

Rated Closing Coil Voltage : 250 VDC

LIGHTNING ARRESTOR / SURGE DIVERTER : Over voltages may occur in sub-station byincident of traveling wave from transmission line due to lightning impulse with steep wave front inthe range of 1/50 s.

Temporary over-voltages (TOV) may be caused by a number of system events such as line toground fault, circuit back feeding, load rejection, ferro-resonance etc . There may also be otherinternal surges known to be switching surges due to current chopping, successive restrike byinterruption of capacitive current etc .

A lighting arrestor resembling a safety valve of the system diverts these over-voltages to ground bylowering its resistance, and also interrupts power frequency follow up current by developing its ownresistance to high value as soon as the voltage comes to normal value .

LAs are of two different types:-

(a) The old valve type arrestor consists of a stack of spark gaps and resistor discs . This resistance,which goes by different names like metrosil, thyrite etc. has a non-linear volt-ampere characteristic,and its ohmic value decreases very rapidly with increase of voltage . The power frequency follow-upcurrent reduces after subsidence of voltage to normal value and is broken by the spark gaps at the firstcurrent zero .

(b) In modern gapless arrestor zinc oxide valve elements are used, which are composed of acompound of zinc oxide and small amount of other selected metal oxides . These ingredients aremixed in powdered form, pressed and sintered to form a polycrystalline ceramic disc . Themolecular structure is a matrix of highly conductive zinc-oxide grains surrounded by resistiveinter-granular metal oxides . Under electrical stress, this inter-granular layer conducts giving highlynon-linear characteristic .

The residual discharge voltage of a LA is the most important characteristic, which decide theprotective margin the LA provides to sub-station equipments, and must be below the BIL of the Sub-


49/58

station . The difference of residual voltage and BIL denoting the protective margin should be at least20% . The residual voltage is the voltage across the LA while discharging an approaching wave andspecified by the manufacturer for different wave front shapes and current values like lightningimpulse voltage (8x20 s, 5,10 & 20 KAP) , switching impulse voltage (30 x 60 s, 1000 AP), steepcurrent impulse at 10KAP .

The arrestor rating is selected on the basis of highest system voltage (MCOV =1.1 x nominal line toline voltage) and the co-efficient of earthing, where the value of the latter is 0.8 for effectively earthedsystem and in between 0.8 & 1.0 for non-effectively earthed system . In a 220KV effectively earthedsystem, the rating should not be less 245 x 0.8 =196 KV.

The distance of LA from transformer is important on the consideration of whether the maximumvoltage attained at the transformer terminal remains within safe limit after reflection at the terminal. Awave with a same rate of voltage rise as the original wave and with a magnitude equal to arrestorresidual discharge voltage builds up at double rate until it reaches to a maximum value of twice thedischarge voltage or to whatever voltage can build up during the period the reflected wave travelsback to LA and a reflection travel back to the transformer .

Modern LAs are very fast to interrupt the follow-up current . The time taken for this function to becompleted is hardly half-cycle before the sensing time of tripping relays.

EARTHING: There are two types of earthing (a) System earthing (b) Equipment or body earthing.The neutral point of a starconnected system is earthed to avoid floating neutral condition andconsequent over stressing of equipment by over voltage during unbalanced loading . Such earthingalso ensures effective relaying and protection by increased fault current . An ungrounded high voltagesystem will lead to a capacitive fault current through earth, which gives rise to a condition known asarcing ground, in which cycle of charging and discharging of the system capacity through the faultresults in high frequency oscillation and a build up of high voltage .

In an unearthed system, insulation level to ground should be of high value approaching to line to linevoltage to cope with the voltage during single phase to ground fault condition and therefore the cost ofinsulation is higher .

When the system neutral is directly grounded without any impedance, the system is said to beeffectively grounded . Here the combined impedance of equipment, circuit and earth return path isconsidered sufficient to limit the-fault current .

However, when a current limiting device like resistance, reactance or arc suppression coil is used in agrounding circuit, the system is said to be non-effectively earthed .

Reactance acts as a neutralizer of capacitive component of the fault current, and as an arc suppressorand ensures satisfactory relaying, partial grading of apparatus insulation, and reduced communicationinterference as compared to that in effectively grounded system .

EQUIPMENT EARTHING: Under fault condition, the non-current carrying metal parts attains ahigh potential at the fault location, and a potential gradient is developed along the path of the faultcurrent which includes metallic part of the equipment and earth return path through soil . To limit thetouch voltage along the metallic surface of the equipment and step voltage along the soil surfacearound the equipment, the non-current carrying metallic parts are connected to the general mass ofearth by multiple electrodes .


50/58


51/58


52/58

flows in both directions as good as normal bus . It is normally a single winding auto-transformerhaving voltage taps corresponding to bus voltages at the two sides and is either in 3 or in 1 construction . As the ratio of bus voltages is near 1, auto-transformer is the economic solutionof voltage transformation by saving of copper . The saving increases as the ratio approaches to one . The scheme envisages saving also in core for less window area and in volume of tank . While havingthe same constructional and protective features as that of a conventional power transformer, IBT isnormally equipped with on-load tap changer to control voltage and consequent reactive power flow .

As the two voltage sides of such auto transformer are in star-star configuration, a delta connectedtertiary winding is incorporated for equalization load in three phases during unbalanced load, asattained by circulation of induced current through closed delta . The delta tertiary also provides aclosed path for third harmonic current, which reduces distortion of wave shape . Power may also bedrawn from tertiary windings .

PROTECTION: Different protection schemes employed in EHT Substation are typically as follows.The schemes vary according to equipments, the bays are equipped with.

INTER BUS TIE TRANSFORMER :

(a) Transformer percentage biased differential relay - The relay operates on current balance principle . However, as such relay suffers from instability by inaccuracies of CTs of two ends with resultingdifference of magnetizing current during through-fault or even during normal load condition; suchrelay is biased with restraining winding . Percentage bias setting varies from 5-50% and relay current10-100% of full load . Sometimes stabilizing resistances are also used in series with the operating coilto eliminate the use of restraining winding. Such biasing leaves certain percentage of windingunprotected and taken care of by restricted earth fault relay .As magnetizing in-rush current during energisation of transformer tends to operate a differential relay,stability is attained by providing 2 nd harmonic restraint feature, where 2 nd harmonic filtered current isfed to a restraint coil .

(b) Circulating current differential relay It also operates on circulating current principle , though onlyon three terminal currents of single winding . As there is no isolation between primary and secondarywindings in this case, the phenomenon of magnetizing current in rush does not affect its operation,and no harmonic restraint is required . Also instead of any restraining coil, a resistance is put in serieswith the operating coil for stabilization of the relay .

(c) Over-current and earth-fault relay O/C & E/F relay with both IDMT and instantaneous features are incorporated at both voltage sidesand tertiary side.

(d) Neutral O/C relay The IDMT O/C element measures the current through neutral of the transformerto protect against earth fault .

(e)

Over fluxing relay This relay, which measures the ratio of voltage and frequency ( = K.E/f) isprovided with time delay element at the both voltage sides of the transformer.

LINE PROTECTION:

Distance Relay: It is a stepped distance scheme with three time delayed zones of protection . Thezone-1 is set to reach about 80%, zone-2 130% and zone-3 200% . One set of two mho elements for1st & 2 nd zones and one offset mho for 3 rd zone is used for phase fault and another separate set for


53/58


54/58


55/58

INSTRUMENTATION & SAFETYINSTRUMENTATION & SAFETYINSTRUMENTATION & SAFETYINSTRUMENTATION & SAFETY PRECAUTIONSPRECAUTIONSPRECAUTIONSPRECAUTIONS

DVC DTPS is well equipped with the instrumentation system. The instrumentation system Is animportant part of the plant and without it the power plant cannot run. There are thousands of pressuresensors, temperature measuring instruments in the plant. The temperatures are sensed by sensors.There are also oxygen sensors, and conductivity sensors. All these sensors are example ofinstrumentations. Again it is almost impossible to keep all the meters under notice since there are lotsand lots of measuring meters in the whole power plant. To avoid this problem, a control panel isestablished. This control panel takes notice of all the measuring meters and gives feedback to theconcerning body and the person who is in charge. These sensors are generally equipped with microprocessor and microchip.Amongst many, an important instrumentation unit is the Turbine SupervisoryEquipment.

LABORATLABORATLABORATLABORATORORORORY AND SECURITYY AND SECURITYY AND SECURITYY AND SECURITYDTPS is well equipped with laboratories. There is a Coal Analysing Laboratory, A Chemical analysisLaboratory an several others. These laboratories help is analyzing the characteristics of the water andthe coal and also oil. There are equipments to measure the grain fineness of the coal. There are alsoinstruments that help is measuring the amount of volatile materials in the coal. The main equipment inthe coal analysis laboratory is Autoproximiser. There is also a VM Analyser, Bomb calorimeter formeasurement of calorific value of coal and an Ash calorimeter. Ash determination is also done bymuffle furnace. These instruments and laboratories are essential part of DTPS and its properfunctioning.

The security system of the plant is controlled by CISF . They take care of any unwanted hazards andalso give the safe guard for fire prevention through their Fire Station unit.


56/58


57/58

ENVIRONMENTAL ASPECTENVIRONMENTAL ASPECTENVIRONMENTAL ASPECTENVIRONMENTAL ASPECT

DTPS always takes care of the environment and makes sure that

no environmental policies are violated. The thermal power plantemits ash, CO 2, SO 2, NO x etc and discharge liquid effluentscontaining oil, grease, chemicals, resins, and dirt. The emitspollute the air and the foul air causes sore throat, respiratorytrouble, stinging eyes etc. Thermal inversion during winter causesthe cooler polluted air trapped near the ground by the warmerupper layer to get cooked by the sun rays to form a layer of O 3 which damages vegetation and effects human lungs. SO 2 chemically reacts with marble and lime stone and tends to destroybuildings. Organic effluents may contaminate aquifers andsurface water bodies. Untreated sewage and hot water may spoilaquatic living creatures In water courses. Liquid effluents maycontaminate land and water, destroying the fertility of land andportability of water.


58/58

CONCLUSIONCONCLUSIONCONCLUSIONCONCLUSION

The practical experience that we gathered during the training isvery helpful in our coming practical life. It gives us very widespectrum to utilize the theoretical knowledge to put into practice.The trouble shooting activities during the operation and decisionmaking in case of crisis make us confident to work in industrialatmosphere.Moreover, working in the industry along with Engineers, workers,staff members, and superiors give us a chance to enhance our

interpersonal relationship.

D.T.P.S, D.V D.T.P.S, D.V D.T.P.S, D.V D.T.P.S, D.V .C..C..C..C.

Final Project on power plant

Documents